1. Field
Embodiments relate to a battery pack, and more particularly, to a high power and high capacity battery pack including a plurality of unit batteries.
2. Description of the Related Technology
Secondary batteries, unlike primary batteries, are rechargeable. Low capacity secondary batteries are used in small portable electronic devices such as phones, notebook computers, camcorders and other similar small portable electronic devices. High capacity secondary batteries are widely used as motor-driving power sources of hybrid vehicles.
Such secondary batteries include cylinder type batteries and prismatic type batteries. In order to drive a motor of a device requiring high capacity, e.g. a motor of an electric vehicle or a hybrid vehicle, a plurality of high power secondary batteries are connected in series to constitute a high capacity secondary battery.
As such, a single high capacity secondary battery, i.e., a battery module, includes unit batteries that are connected in series. Each of the unit batteries includes an electrode assembly having a positive electrode plate, a negative electrode plate, and a separator therebetween, a case receiving the electrode assembly, a cap assembly coupled to the case to close the case, and positive and negative terminals. The positive and negative terminals protrude from the cap assembly and are connected electrically to collectors of the positive and negative electrode plates provided to the electrode assembly. Thus, the unit batteries cells of the battery module are spaced apart from each other and are connected in series or in parallel through electrode tabs. The battery module is inserted into a spacer separating the unit batteries apart from each other. The battery module is electrically connected to a protective circuit module and is disposed in an outer case to constitute a battery pack.
In the battery pack described above, lead wires extending from the protective circuit module contact the unit batteries because a structure for distributing the lead wires is not provided. Thus, when the unit batteries are overheated, the lead wires may melt or become welded so as to contact each other or the unit batteries, and the protective circuit module fails to work.
In addition, when a position where the lead wire extends from the protective circuit module is disposed on an opposite side to a position where the lead wire is connected to the unit battery, it is difficult to distribute the lead wire. Furthermore, since the lead wires extend along connection portions of the unit batteries, the extension lengths of the lead wires are increased, and thus manufacturing costs are increased.